Also, TexNotes has the ability to export their notes in a variety of very flexible ways, including plain text and rtf.
i also think it would be a great idea to be able to store the data from a notetaker in an open way. however, on the programmer's side I think it may be a slightly unreasonable request. Especially when it comes to organizing and all the other things the notetaking program does. I just think it's asking too much to retain all the notetaking features in some kind of open way where it can be imported/exported to other programs. but if all you want to be able to do is READ the notes and their contents (and not their organization, linking, fancy formatting, etc.) then there are a couple of programs that do this. Like I said, AM-Notebook can do this.